1. Field of the Invention
This invention relates to a method of detecting immunological agglutinating reaction.
2. Description of the Prior Art
As an example of the prior art method of determining blood group, the method disclosed by U.S. Pat. No. 3,883,308 granted to Claude Matte (to be referred to as "Matte", hereinafter) will be briefly reviewed. The method of Matte comprises steps of pouring certain amount of a centrifugated suspension having 2 to 5% of blood corpuscles to be analyzed and a specific antiserum into a reaction vessel having a curved bottom of brandy glass shape, agitating the suspension and the antiserum, keeping the reaction vessel standstill, effecting centrifugal precipitation, applying a special high-speed shake-up to the reaction vessel so as to disperse the precipitated blood corpuscles, agitating the reaction vessel comparatively slowly so as to collect agglutinates at the central portion of the bottom of the reaction vessel for producing an agglutinates pattern at the bottom of the reaction vessel, and detecting the agglutinates pattern by photometry. This method is based on a phenomenon that, after the aforementioned shake-up and comparatively slow agitation, particles combined by agglutination are quickly collected at the central portion of the reaction vessel while non-agglutinated particles are dispersed again in the suspension and not collected at the central portion of the reaction vessel. To detect the agglutinates pattern formed at the central portion of the bottom of the reaction vessel, a photoelectric measurement such as nephelometry or opacimetry is used; namely, when luminous flux passes through the suspension, the degree of light absorption by the suspension varies depending on the density of the blood corpuscles suspended between the top surface of the suspension and the bottom of the reaction vessel, which variation of the light absorption is photoelectrically measured as different degrees of turbidity. More particularly, in the example of FIG. 33 of Matte, luminous flux is directed from above to the reaction vessel having a transparent bottom of brandy glass shape, and a mask plate or a bottom plate having a central aperture and an annular aperture around the central aperture is disposed below the reaction vessel in such a manner that, light coming through the central aperture is applied to a first light-receiving element while light coming through the annular aperture is applied to a second light-receiving element through a lens. Thus, the amount of light incident to the first light-receiving element after passing through the central portion of the reaction vessel represents the turbidity at the central portion of the suspension being analyzed, while the amount of light incident to the second light-receiving element after passing through the peripheral portion of the reaction vessel represents the turbidity at the peripheral portion of the suspension being analyzed. Accordingly, if the amount of light of the light passing through the central portion of the suspension being analyzed decreases as compared with its reference value and at the same time the amount of light of the light passing through the peripheral portion of the suspension increases as compared with its reference value, "presence of agglutination" is determined. On the other hand, if the amounts of light of the lights passing through the central portion and the peripheral portion of the suspension being analyzed remain unchanged as compared with their reference values, "absence of agglutination" is determined.
The conventional method of detecting and determining the agglutinates pattern, as exemplified by Matte, has a number of shortcomings. Namely, the reference values of the amounts of light for the first and second light-receiving elements must be calibrated and set beforehand, by using a suitable reference agglutinates pattern, which calibration and setting tend to make the operation of the determination cumbersome. Besides, the reference agglutinates pattern is not necessarily identical with actual agglutinates patterns of the suspensions to be analyzed, so that the deviation of the reference agglutinates pattern from the actual agglutinates patterns tends to cause an error in determination of the presence or absence of agglutination. Moreover, the conventional method requires to prevent that part of the luminous flux incident to the peripheral portion of the suspension which is scattered by particles therein from reaching the first light-receiving element through the central aperture of the mask or bottom plate, and to prevent that part of the luminous flux incident to the central portion of the suspension which is scattered by particles therein from reaching the second light-receiving element through the annular aperture of the mask or the bottom plate. Accordingly, the mask or bottom plate and the first and second light-receiving elements must be so constructed and disposed as to meet the aforementioned requirements, which construction and disposition tend to make the optical system for detecting the light absorption complicated and difficult to manufacture.